The incidence of seizures is highest in the first decade of life and status epilepticus is more common in children than adults. Animal studies have also demonstrated that the immature brain is more prone to seizures than the adult brain, presumably secondary to a developmental imbalance between maturation of excitatory and inhibitory circuits. In addition to the increased risk for epilepsy in children, there are some suggestions that seizures during early development may be more detrimental than those occurring in the mature brain. Onset of non-febrile seizures during the first years of life are significant predictors of poor neurological outcome. The poor prognosis following seizures in young children may be related to the seizures themselves, the underlying etiology of the seizures, antiepileptic drug treatment, or all three. Despite the seriousness of the problem, there have been few studies assessing the benefit and safety of antiepileptic drugs (AEDs) in this age group. This deficiency was recognized by a consensus conference in a recent NIH workshop on AED drugs in children. In this planing grant application we are seeking support for one year to design a randomized clinical trial of AED therapy in children with epilepsy at risk for adverse developmental outcomes and intractable epilepsy. Children between the ages of 1 month to 3 years with frequent seizures and abnormal EEGs will be randomized to one of four AEDs. The treatment goal will be seizure freedom or a greater than 80 percent reduction in seizure frequency from baseline. Children not meeting this treatment goal will be changed to a second study drug. In addition to comparing efficacy and safety of AEDs in young children, we wish to examine those factors that predict both poor developmental outcomes and intractable epilepsy. We are hopeful that this study will provide a template for future studies evaluating therapy in severe childhood epilepsy.